1. Field of the Invention
Implementations of various technologies described herein generally relate to methods and systems for attenuating noise in seismic data.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Implementations of various technologies described herein generally relate to methods and systems of processing seismic data. Seismic data may be acquired in a seismic survey. In a seismic survey, a source may be activated to generate energy, which may be reflected back by the earth's sub-surface layers. The resultant seismic wavefield may be sampled by an array of seismic receivers disposed at a distance from the seismic source. Each receiver may be configured to acquire seismic data, which is normally in the form of a record representing the value of some characteristic of the seismic wavefield against time. The data received by a receiver and then recorded are collectively called a seismogram. Information about the earth's sub-surface can be obtained from the acquired seismic data.
In addition to information about the earth's sub-surface, the acquired seismograms may contain noise. The noise may reduce the accuracy of the information about the earth's sub-surface obtained or derived from the seismic data. The noise may come from various sources. For example, noise may be acquired in marine seismic data acquisition due to waves propagating along streamers used during marine seismic data acquisition. Noise may also be acquired from other vessels acquiring seismic data or drilling activity in a relatively close proximity to the survey area. Noise may also be acquired during land seismic data acquisition from sources such as ground-roll or air-waves.
In some circumstances, a portion of the noise may be filtered from the signal and the resulting filtered signal may be used to obtain information about the earth's sub-surface. Using a filtered signal, rather than an unfiltered signal, may increase the accuracy of the information about the earth's sub-surface derived from the signals.
One technique of filtering noise from a signal (e.g., a seismogram or a trace) is to use a band-pass filter. A band-pass filter may be configured such that desirable frequencies of the signal pass through the filter without being attenuated while undesirable frequencies (e.g., noise) are attenuated when the signal passes through the filter.
Although noise filtering (e.g., band-pass filtering) may attenuate some of the noise from the signal, the level of attenuation, or the amount of noise filtered from the signal may not be sufficient. That is, the filtered signal may still contain some noise, and thus the filtered signal may not increase the accuracy of the information regarding the earth's sub-surface to an acceptable level. Therefore, there exists a need for methods or systems designed to reduce more noise or do a better job of attenuating noise from seismic data signals.